/**
 * Example using a port.
 * Copyright (c) 2011, Nycholas de Oliveira e Oliveira <nycholas@gmail.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * * Neither the name of the Nycholas de Oliveira e Oliveira nor the names of
 *   its contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
#include <stdlib.h>
#include <stdio.h>

typedef unsigned char byte;

int read_cmd(byte *);
int write_cmd(byte *, int);

int main(void) {
    int fn, arg1, arg2, result;
    byte buff[100];
    
    while (read_cmd(buff) > 0) {
        fn = buff[0];
        if (fn == 1) {
            arg1 = buff[1];
            arg2 = buff[2];
            
            //fprintf(stderr, "calling sum %i %i...\n", arg1, arg2);
            result = sum(arg1, arg2);
        } else if (fn == 2) {
            arg1 = buff[1];
            arg2 = buff[2];
            
            //fprintf(stderr, "calling subtract %i %i...\n", arg1, arg2);
            result = subtract(arg1, arg2);
        } else if (fn == 3) {
            arg1 = buff[1];
            arg2 = buff[2];
            
            //fprintf(stderr, "calling multiplies %i %i...\n", arg1, arg2);
            result = multiplies(arg1, arg2);
        } else if (fn == 4) {
            arg1 = buff[1];
            arg2 = buff[2];
            
            //fprintf(stderr, "calling divides %i %i...\n", arg1, arg2);
            result = divides(arg1, arg2);
        }
        
        buff[0] = result;
        write_cmd(buff, 1);
    }
    
    return 0;
}